how to open jar files in windows 7

I have a jar file which used to work in Win XP, but doesn't in Win 7. I get a message "Could not find main class: C:\users\<file path>. Program will exit."

I don't really understand jar files, but looking around the main solution seems to be the need for a 'manifest file'...which doesn't help me because a manifest file already exists and appears to define the main class.

normally jar files are of two types executable jars and non executable jars non executable jars will need to be run from a program so it shud have a main class in it. But i presume this is a executable one but use a jaav jdk to make it executable u can try unrar the jar file or converting the existing jar file to executable one.

If you install the Java Runtime Environment or if you already have the Java Runtime Environment then you have follow this steps to open the Jar files in Windows:-

1) Open the Windows Explorer and click on the menu bar of Tools and the select the Folder Options.
2) Now click on the sub-tab option File Types.
3) Now select the Jar option from the list.
4) Now click on Advanced button.
5) Now select the Action button and then click on Edit button.
6) Now click the Browse button and select the Java Interpreterjavaw.exe.